Study of the TiO to Anatase Transformation by Thermal Oxidation of Ti Film in Air

Abstract

The TiO to anatase phase transformation has been studied by transmission electron microscopy in this Article. It is shown that prior formation of TiO from Ti film can induce the formation of anatase by thermal oxidation in air; otherwise only rutile is formed. Ti film deposited on the NaCl (001) surface is induced to form epitaxial TiO film by thermal oxidation in air. Further thermal oxidation in air partially transformed TiO into anatase (A) with a parallel orientation relationship of {200}A//{200}TiO. Detailed analysis of the lattice fringes image of the specimen reveals the presence of very high density of misfit dislocations. The TiO to anatase transformation is reversible as further annealing in a vacuum can turn the anatase back into TiO and eliminates the misfit dislocations. The transformation is analyzed in terms of the crystal structure, orientation relationship, and the dislocation distribution, which show that the TiO to anatase transformation is due to the close similarity between their structures.

The formation of anatase TiO2 from TiO nanocrystals in sol–gel process

“…This result is consistent with the previous results that TiO can lead to the formation of anatase [1,5,6]. In the previous cases of oxidation of TiO film [1] and anodized TiO film [6] the parallel orientation relationship of {100} TiO //{100} anatase between TiO and anatase was observed because epitaxial TiO films were used so that the TiO and anatase interfaces could be located. However, in the present case of randomly oriented TiO nanocrystals, the orientation relationship could not be observed.…”

“…Further annealing at higher temperature in air turned the TiO into anatase with a parallel orientation relationship of {100} TiO //{100} anatase . That TiO can lead to the formation of anatase was attributed to the close similarity between their structures [1]. Other reports also confirmed that if TiO was formed first in vacuum deposition processes then anatase could be formed by subsequent thermal oxidation [2][3][4].…”

“…It was routinely prepared by vacuum deposition, anodization of Ti and Ti alloys, and solgel methods. Recently it was shown that the prior presence of TiO is essential for the formation of anatase [1]. Without the prior formation of TiO, no anatase but only rutile was formed.…”

Size, Composition and Structural Changes of TiO2 Rutile Nanoparticles by Pulsed Laser Ablation in Water

“…In any case, anatase may be stabilized by Ti 2+ in view of the TiO to anatase transformation by thermal oxidation of Ti film in air under the influence of NaCl template. 7 The 2 × 110 superstructure of rutile 44 45 The (Ti 3+ , Ti 2+ , H + )-codopant may also reside on the surface sites of TiO 2 nanocrystals for surface disordering, color change and band gap lowering. In fact, the disorderengineered darkish nanophase TiO 2 with narrowed band gap has been prepared by static aqueous solution from other precursor material to consist of two phases, i.e., a crystalline (anatase) TiO 2 quantum dot or nanocrystal as a core, and a highly disordered surface layer where dopants are introduced.…”

Evaluation of Photocatalytic Activity of the TiO2 Layer Formed on Ti by Thermal Oxidation

“…Shabalin et al [42] presented an oxidation model of TiC, in which incorporation of carbon in TiO 2 stabilized the anatase phase. Meanwhile, Kao et al [44] observed the reversible transformation between TiO having an NaCl-type structure and anatase. They pointed out the similarity between their structures: TiC and TiN exhibit NaCl type structure with a lattice constant close to TiO; the anatase formation on TiC and TiN in thermal oxidation would be related to this NaCl-type structure.…”